[Wayland-bugs] [Bug 97379] Wayland buffer synchronisation is undocumented

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97379

            Bug ID: 97379
           Summary: Wayland buffer synchronisation is undocumented
           Product: Wayland
           Version: unspecified
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: wayland
          Assignee: wayland-bugs at lists.freedesktop.org
          Reporter: tomek.bury at gmail.com

Wayland silently assumes implicit cross-process fencing on shared buffers. This
assumption goes beyond EGL/GLES core spec and any Wayland extension but is not
specified anywhere.

It would be much easier for driver or compositor authors to have very clearly
spelled out requirements and guarantrees, especially around shared resources.

Current mechanism, as far as I understand it, looks rather weird: EGL is
responsible for handing a buffer over from client to compositor, but EGL is not
involved (and completely unaware) of handing buffer back to client.

As it's pretty much guaranteed that drivers and compositors will come from
completely unrelated parties and can be mixed and matched, implicit assumptions
in this area must lead to interoperability issues and a lot of confusion as to
what is valid or invalid behaviour.

Could you clearly document responsibilities and guarantees of both driver and
compositor in buffer management, including CPU-GPU synchronisation please?

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